AAA,
You are right most--if not all--hedge funds are private placements which are exempt from state and federal registration. However, as you probably know, each state has its own disclosure requirements--even for private placements--and many require the filing of certain documents (i.e., Blue Skying Reqts) even though its not an actual "registration." Reg. D also requires certain disclosures and the filing of Form D.
Document preparation costs and filing fees vary greatly depending on the funds primary jurisdiction, the number of states where the fund intends to solicit investors, whether the fund will incorporate futures products in its investment/trading strategy (i.e., whether the fund will also require registration as a commodity pool) and the structure of the fund (i.e., master-feeder, fund of funds, multiple classes of shares, etc.). I'm sorry I can't be more specific on the costs in this forum.